A pedestrian walks past photographs and flowers placed at a memorial for Canadian actor Cory Monteith outside the Fairmont Pacific Rim Hotel in Vancouver, British Columbia, Monday, July 15. Officials in British Columbia, where Mr. Monteith grew up and where he died at the age of 31 at a hotel on Saturday, warned this week of a recent spike in deaths related to heroin.

The overdose death of “Glee” star Cory Monteith has put a spotlight on an alarming rise in the number of young people becoming addicted to heroin – and dying from its effects, particularly in combination with alcohol or other drugs.

An earlier surge in prescription drug abuse – and the recent crackdown on that trend – is one of the key factors behind increased heroin addiction, drug-abuse experts say, explaining that often, those who use prescription drugs in search of a high start to see heroin as a cheaper way to hit those highs or to stabilize withdrawal symptoms.

A large share of the emerging new heroin users are 18-to-25-year-olds, many of whom are white and middle class.

A rise in overdoses and related deaths are partly related to this spike in newer users of heroin, “who have not yet developed the strong tolerance to the drug that more traditional longtime users would have,” says James Hall, an epidemiologist at the Center for Applied Research on Substance Abuse and Health Disparities at Nova Southeastern University in Davie, Fla. Without that tolerance, he says, the new users are more vulnerable to even mild increases in the purity of the street drug.

There’s also been a rise in a combination of drugs being involved in overdose deaths, Mr. Hall says. Even if heroin is not taken simultaneously with alcohol or prescription drugs, the presence of those substances in the system can increase the combined toxicity.

Officials in British Columbia, where Mr. Monteith grew up and where he died at the age of 31 at a hotel on July 13, warned this week of a recent spike in deaths related to heroin laced with the drug fentanyl. But the coroner reported that Monteith’s death did not involve fentanyl.

The number of people who abused or were dependent on heroin increased from 214,000 in 2007 to 426,000 in 2011, according to the National Survey on Drug Use and Health, reported by the US Department of Health and Human Services.

More recent statistics are available from regional experts around the country who track trends for the National Institute on Drug Abuse (NIDA). Recent increases in heroin problems were reported in at least 11 areas of the country, ranging from Minneapolis to Atlanta, says Hall, a member of the NIDA group.

In South Florida, which Hall monitors, the number of heroin deaths jumped 60 percent between 2010-11 and 2011-12. In the 35 heroin deaths there in the first half of 2012, all but one involved additional substances.

In Texas, both supply and demand indicators for heroin have been increasing, and the average age of those dying from heroin overdoses dropped from 40 to 36 in five years, according to Jane Maxwell, a University of Texas epidemiologist in the NIDA group.

In Washington State, among 18-to-29-year-olds, more treatment is now sought for heroin abuse than for alcohol abuse. “That’s a stunning and very rapid change,” says Caleb Banta-Green, a research scientist at the Alcohol and Drug Abuse Institute at the University of Washington who has studied the links between prescription drugs and heroin.

In 2012, among high schoolers surveyed in the state who had used prescription opiates to get high in the past month, 23 percent had used heroin at some point. Among those not using prescription drugs to get high, only 3 percent had ever used heroin.

Efforts to crack down on the availability and abuse of prescription drugs in recent years made it easy to anticipate a rise in heroin use, says Eliza Wheeler, program manager at the Harm Reduction Coalition in Oakland, Calif. Policymakers should have anticipated that and built in “more access to treatment, to overdose prevention, and to HIV/Hepatitis prevention,” she says.

The problem of drug overdoses and deaths extends far beyond the use of heroin or other illicit drugs. In the United States, drug abuse was the leading cause of injury and death in 2010, according to the Centers for Disease Control and Prevention. Of the roughly 38,000 drug overdose deaths that year, 60 percent were related to pharmaceuticals; 78 percent or more were unintentional.

To tackle these problems, society needs to address the “huge disconnect between what we know about addiction and what we do to address it,” says Susan Foster, vice president of CASAColumbia, a substance-abuse research center at Columbia University in New York.

Monteith’s story of struggles with addiction starting in his youth – which he had sought treatment for as a 19-year-old and again as recently as April – is fairly typical: about 95 percent of addictions start with substance abuse in the teen years, Ms. Foster says.

Instead of seeing “risky use as a rite of passage,” she says, people need to better understand that the risk of addiction is about six times greater for young people, whose brains are still developing, than if they first use substances when they turn 21 or older.

Secondly, Foster says, when people do have treatment, it’s often not based on up-to-date science on what can most help them recover from their addictions.

Drug-abuse prevention and treatment has been separated from the medical community, and there need to be more bridges, Foster and others say.

“People want to think of addiction as acute – you go and get fixed – but it takes a long effort,” Ron Jackson, an expert on drug abuse and treatment at the University of Washington in Seattle. Addiction goes beyond physical dependency and becomes an emotional attachment, he says. “It’s difficult to break that…. Think of the thing most dear to you and having to walk away from that.”

While many efforts are being made to prevent addiction or help people recover, there are also advocacy groups working to educate people about how to reduce overdoses among those who continue to struggle with drugs.

Some states have Good Samaritan laws to encourage people to call 911 to help in an overdose situation without fear of being arrested.

A movement is also afoot to increase information about naloxone, a drug that reverses potentially fatal breathing problems associated with opioids, including heroin.

Since the mid-1990s, more than 10,000 deaths have been prevented through training more than 53,000 people to administer the drug, according to the CDC. Since that survey of about 50 programs in 2010, the number of programs promoting naloxone use has risen to about 200 nationwide, Ms. Wheeler says.

In Monteith’s case, as in many overdose situations, he appears to have been alone when he died, according to police.

Amid the alarming statistics on heroin use, one bright note is that, for the first time, Mr. Banta-Green in Washington has seen a decline in the number of high schoolers using prescription opioids (down from 10 percent in 2006 to 6 percent in 2012).

“Reining in the prescription drugs hopefully will prevent or help to slow down a new generation in terms of getting addicted,” he says, “but in the meantime, for the people who are 20 who are already addicted, we still have to take care of them for the next 50 or 60 years.”